It's not that all the best sci-fi movies are rated R, but it is one of those genres that, like horror, thrives when its given permission to get down and dirty. Which makes sense, considering sci-fi is all about ideas, and ideas are at their best when they're given room to push the boundaries of comfort. While the realm of family-friendly sci-fi has delivered some of the best entertainment of all time, when you take the brakes off, you end up with some of the most vital filmmaking in the history of cinema.

As I testament to how rich this particular subgenre is, this list just kept spilling out in new directions. I'd cement my picks and remember a fantastic film that slipped me by, only to rearrange the list and remember yet another gem. As far as the ranking... I mean, forget it. There are, in my estimation, no less than fifteen of the best films ever made on this list. I tried to consider all angles when lining up the ranking -- storytelling, direction, technical invention, impact, influence, the list goes on -- but ultimately, it's going to come down to a bit of personal preference.

A few notes on the films you won't find below. This list is restricted to live-action films, so there's no Akira or Ghost in the Shell (but you can check out Dave's kick-ass list of cyberpunk animated movies here). It's also restricted to films that are technically R-rated, so Unrated or NR classics like Battle Royale and Upstream Color. I also tried to restrict the choices to films where the sci-fi element has a major bearing on the plot, message, or form of the film so some beautiful films that are only tangentially sci-fi didn't make the cut.

For the curious, here's the breakdown of the directors with the most hits on the list: Paul Verhoeven (3), David Cronenberg (2), Ridley Scott (2), John Carpenter (2), Terry Gilliam (2), and George Miller (2). But the biggest winner? Alex Garland, with a grand total of 4 movies between his screenwriting and directorial credits.

Check out the full list below, and be sure to sound off in the comments with your favorites, and like I said, don't get hung up on the rankings. It's an impossible task, and this is really just about celebrating one of the best and most fruitful subgenres in cinema. Enjoy!

38. Perfect Sense

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Image via IFC Films

Where most sci-fi takes aim at the mind, Perfect Sense directly targets the heart with a lusty love story set against the backdrop of the apocalypse. Directed by genre chameleon David McKenzie (Hell or High Water), the film centers on a chef (Ewan McGregor) and an epidemiologist (Eva Green) who meet and fall in love in a sleepy Glasgow suburb as an unprecedented plague sweeps the world, slowly depriving humanity of its senses. The loss of each sense is preceded by a flurry of emotion. The first assault of the virus takes the sense of smell in a wave of deep despair, then goes taste in a wash of ravenous hunger. So it goes until humanity is completely upended, left on with sight and the promise of looming darkness.

The end of the world shares the spotlight with Michael and Susan's love story. Both are self-involved emotionally distant lovers, only half joking when they dub themselves Mr. and Mrs. Asshole. Were it not for the end of the world, they almost certainly would never have come together so fiercely and so intimately. Theirs isn’t a love for the ages; it’s a love for the end of days. Fitting to the subject matter, Perfect Sense is a perfectly sensual experience as McKenzie explores the wonders of human perception through the heightened awareness of two people falling in love. A bit bleak, but ultimately a moving Perfect Sense is soft where most sci-fi is hard, swapping bedrooms for battlefields and lovers quarrels for explosions, but hitting hard all the same as we see the world reach its end through the eyes of two lovers who wish they had an eternity.

37. Timecrimes

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Image via Magnolia Pictures

The first of many time travel mind-benders on the list, Nacho Vigalondo's spanish language feature debut will run your mind into the ground with logic loops if you think about it too hard. The events in Timcrimes happen because the events in Timcrimes happen. Once you get past that, Timcrimes delivers a bounty of causal loop time travel deliciousness. The film follows Hector (Karra Elejalde), a married man who glimpses a nude young woman in the woods. After his wife heads out, he ventures out to investigate when he signs of distress and stumbles upon a time machine that sets him on a deadly, cyclical course. Well executed time loop movies are always a delightful puzzle, and director/writer/co-star Nacho Vigalondo concocts a tight time travel puzzle box that finds its protagonist caught in a web of his own design. And perhaps most importantly in these kinds of entertainment-centric mind-benders, he ultimately finds a satisfying resolution.

36. Upgrade

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Image via Blumhouse
As the co-creator and co-star of Saw and InsidiousLeigh Whannell's got some serious horror cred, but the filmmaker broke new ground this year with his sci-fi/action passion project Upgrade. Set in a familiar-looking future, the film stars The Invitation‘s Logan Marshall Green in another scene-stealing performance as Grey Trace, a man left in a quadriplegic state after after a violent attack that kills his wife. When a mysterious tech genius offers him the opportunity to walk again, Grey winds up with a chip in his spine that doesn’t give him his legs back, but helps him find and execute the men responsible for his wife’s murder. Better looking than any microbudget action movie has the right, Upgrade follows Grey’s path to vengeance through the criminal underground of Whannell’s grim future and the writer-director does some fine world-building along the way while Green's physical performance carries the action with his masterfully dissonant use of face and body. Put all the pieces together and  you get a smart, sharp throwback sci-fi actioner that feels pulled from the 90s in all the best ways. — Haleigh Foutch

35. Under the Skin

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Image via A24

Jonathan Glazer’s Under the Skin is a peculiar viewing experience of existential horror. It’s oblique, droning, repetitive and meandering, and yet, there’s a persistent eeriness that lingers long after the movie is over. The film stars Scarlett Johansson as Laura, an alien without empathy for human life who seduces men for unknown reasons, taking them to a pitch black room where they wade into a mysterious pool of liquid that sucks them down, leaving behind floating sacks of skin. When she meets and attempts to seduce a meek disfigured man, she decides to change her path and take agency over her own body, but tragically discovers the body she inhabits exists only as a lure to men, offering her no satisfaction, and ultimately no defense against the carnal desires of others. Under the Skin uses science fiction to tell a horror story about gender dynamics and otherness, and while it can be frustratingly difficult to engage with at moments, it has a staying power that scratches at uncomfortable regions of the mind by exploring objectification, identity and body ownership.

34. Never Let Me Go

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Based on the shattering novel of the same name by Kazuo Ishiguro, Never Let Me Go is one of those barely-there genre films that uses the slightest sci-fi construct for an intensely intimate emotional character drama. A subtle alternate history, the story follows a trio of friends maturing into adulthood at an idyllic boarding school in the mid-20th century where they must learn to accept their role as clones, brought into existence for the sole purpose of providing organ transplants. It's uncomfortable and ponderous subject matter that forces us to ask what we'd be willing to sacrifice to prolong our own lives and how dark we might go once we've made that decision, but ultimately Never Let Me Go is much more spiritual than it is intellectual.

As two of the friends, deeply in love but kept separate from each other for a tragic amount of their short lives, Carey Mulligan and Andrew Garfield are the soul of the film, giving tender performances that claw at your heart with innocence and earnestness. Adapting Ishiguro's infinitely layered novel is no easy task, but sci-fi legend in the making Alex Garland successfully distills the story down to its essence, and director Mark Romanek makes it as beautiful as possible, with major assists from cinematographer Adam Kimmel and composer Rachel Portman. It's stunning, stripped-down sci-fi that uses the trappings of the genre to shine a light on what it means to be human, to have a soul, and to make the most of our time on earth.

33. Snowpiercer

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In an attempt to fix global warming, humanity dooms earth to a new ice age where a high-speed train runs on an infinite loop, shepherding the last remnants of the human race through the deadly cold. Such is the set up for Bong Joon-ho's Snowpiercer, adapted from the French comic book Le Transperceneige, which stages a violent revolution in the passenger cars of the ever-moving trains. The passengers who had economy tickets are stuck in a cabin of squalor, starving and desperate, while the first class passengers live in opulent indulgence. When the starving masses reach their breaking point, as starving masses tend to do, they stage a ferocious revolt, hacking their way through the train cars in the hopes of toppling the unjust post-apocalyptic class system.

Chris Evans is cleverly cast as the anti-Captain America, Curtis, the man leading the charge. He's a reluctant revolutionary with a skeleton in his closet so grim it's downright audacious, and he's eager to pass leadership off to his wizened mentor (John Hurt). But once the tide is unleashed, it can't be turned back, and though the people may be pitiful and broken down, they're a force when they're moving together. Each new train car brings a new threat and wild surprises, like one long house horrors, each more visually stunning and outlandish than the last.

32. Sunshine

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Image via Fox Searchlight Pictures

Sunshine is half of one of the best sci-fi movies of all time and half of an OK space horror. It’s all to do with that unfortunate third act twist, which spins an impeccably articulated hard-sci-fi-meets-blockbuster film into a flashy slasher pic, but nonetheless Sunshine is a triumph of the genre. Director Danny Boyle assembled a first-rate cast for his space-bound crew, including Rose Byrne, Cillian Murphy, Michelle Yeoh, Cliff Curtis, Benedict Wong, Hiroyuki Sanada, and Chris Evans (in the first pre-Captain America role that gave him credit for his range of talent). And he puts them to great use in a pulse-pounding, legitimately science-based space adventure for adults that was ever so slightly ahead of its time.

Somewhat of a precursor to hyper-realistic space sagas like Gravity, Interstellar, and The Martian, Sunshine takes the utmost care to endow its characters and circumstances with believability and weight that makes each feel like a piano wire. The greatest strength of that tension comes from the sequences that pit the expert crew against the frivolity of nature and the imperfection of human nature, and while the final act ultimately undermines some of the peak sci-fi that elevates the bulk of the film, it’s still a remarkable achievement that helped chart the course for the future of big-budget sci-fi.

31. They Live

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Image via Universal

One of the finest works of subversion in a decade full of them, John Carpenter's 1988 cult classic They Live is a scathing takedown of yuppie culture and Reaganomics dressed up as an alien invasion actioner. The set up is simple, a boldly cast Rowdy Roddy Piper slips on a pair of special sunglasses and discovers that the world has been overrun by WASPish aliens poisoning the masses with subliminal messages of submission. Then he kicks the shit out of them with Keith David. Along the way, there's an iconic eight-minute back alley brawl, some utterly classic one-liners, and plenty of Carpenter's sharply directed action. They Live is a fantastic combination of clever commentary and low-brow fun, a gutsy anthem to the working man, and downright entertainment.

30. Attack the Block

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Image via Sony Pictures Releasing

The 2011 feature film debut from writer-director Joe Cornish is so good it will make you upset Cornish hasn't directed anything in the years since. Set in a shady South London neighborhood, Attack the Block pits a team of teenage hooligans against “big alien gorilla wolf motherfuckers,” follows the adrenaline-fueled fight for survival that follows. Moses (John Boyega) and his gang are in the middle of mugging a young woman (Jodie Whittaker) when big, furry, neon-toothed aliens start crashing down around them and they take it upon themselves to become the protectors of their neighborhood. The Edgar Wright-produced flick is a pure kinetic rush from beginning to end, Boyega is the find of a decade, and while the phrase "Amblin-esque" gets thrown around a lot, Cornish manages to capture that slippery magic and modernize it.

29. Logan

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Image via 20th Century Fox

While most superhero movies technically fall into the realm of science fiction, there's usually a sheen of high fantasy that keeps them from truly feeling like part of the genre. Ultimately, they make up a genre of their own, something born out of sci-fi but distinct from it. James Mangold's stunning, heartbreaking Wolverine send-off Logan breaks that mold with a grounded approach to genetic mutation, cloning, and Alzheimer's that genuinely pulls the science into the fiction (however far-reaching that science may be). Set in a time long after the heroic antics of the previous X-Men films, Logan finds our titular hero in the Children of Men of mutants, a future where the superpowered genetic anomalies have simply stopped being born. A fantastic and unprecedented genre hybrid, Logan is a sci-fi western superhero movie for adults that takes an unadorned look at the nature and value of heroism, sacrifice, and finding a reason to stay in the fight.

28. Total Recall

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Paul Verhoeven is a master of indefinable films. He delves eroticism, action, and science fiction with a heavily measured tongue-in-cheek satirical bent that is only matched by his unflinching regard for all things beyond the pale. Total Recall, which is one of his finest works, stars Arnold Schwarzenegger as your Average Joe, a regular dude who goes to the local Recall clinic – a place where you can have all the most wondrous memories implanted in your head – and ends up unlocking expertly repressed memories of his life as a secret agent. That pits him against a string of countless government agents, including his stand-in wife (Sharon Stone) as he sets out to bring down a nefarious, if somewhat vague, agency.

Based on a Philip K. Dick short, Total Recall is lavish and ridiculous, a stronghold of Verhoeven’s knack for the extravagant and his willingness to swing for the fences beyond the fences. What it lacks in coherence, it makes up for in pure panache, as Verhoeven explores the wonders of a futuristic society by upending genre conventions as often as it indulges in them. Equally packed with one-liner humor and gory violence, Total Recall is the myth of the Schwarzenneger hero through the twisted lens of Verhoeven, making it true one-of-a-kind in one on the resume of the action genre’s foremost actors.

27. The Mist

A classic B-movie through the lens of three-time Academy Award-nominated writer-director Frank Darabont, the feature film adaptation of Stephen King‘s novella The Mist hits all the beats of a retro monster movie, but opts for candor over camp and fully-drawn characters over archetypes. When a mysterious mist rolls into a quiet East Coast town with giant insectoid monsters in tow, the patrons and employees of the local supermarket are trapped together in a woefully outmatched fight for survival. Known for boasting one of the most brutal endings of all time, The Mist is a genre great thanks to its impeccable cast, Darabont's firm command of the tone and content, and the director's good sense to make the men and women as frightening as the monsters eating them alive. And you've just got to love a movie that has the good sense to let Toby Jones play the unexpected hero

26. District 9

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Image via Sony Pictures

Neill Blomkamp's directorial debut District 9 is the best kind of sci-fi; one that blends technical accomplishment, stylish filmmaking, and looks to a fantastical reality to provide worthwhile commentary on our own. The plot centers on a race of refugee aliens known as Prawns, who land on Earth only to find themselves subjugated and shoved into ghettos. Set in South Africa, the film is rich with Apartheid allegory that Blomkamp embraces without veering into exploitation. Blomkamp also makes magic out of a limited budget with a film that looks outstanding, from the design of his extraterrestrials and their weatherworn technology to his choice of framing device. The film begins mockumentary style and subtly transitions into traditional cinematic POV, making for an experience that slowly draws the audience into the experience and suffering of the Prawns alongside our protagonists. It's a spectacular film about transformation and prejudice, and how quickly the systems of society can turn on that which they deem "other."

25. Blade Runner 2049

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Image via Alcon Entertainment / Warner Bros.

Sure, making a sequel to Ridley Scott's seminal sci-fi classic some 35 years later sounded like a terrible idea on paper, but Denis Villeneuve's meditative sequel is a proud successor to the original that maintains the standards of exquisite visuals and haunted existential ponderings. But Villeneuve doesn't just play copycat, he a new vision of humanity's bleak future pulled from the DNA of Syd Mead's definitive designs, evolved, and brought to life with the extraordinary work of cinematographer Roger Deakins and production designer Dennis Gassner. In the extraordinary hellscapes of humanity's own making, screenwriters Hampton Fancher (who also co-wrote the original) and Michael Green (Logan) dig deep into technological anxieties and spiritual searching that feel even more closely keyed to Philip K Dick's source material than the original film. Richly detailed and a downright marvel to look at, Blade Runner 2049 is an immersive, seriously slow-burn tech-noir searching for soul and the dream of humanity in a piteous future where both are in short supply.

24. Annihilation

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Image via Paramount Pictures and Skydance

Alex Garland proved himself one of the most important voices in contemporary sci-fi filmmaking as a writer long before he got around to making his knockout directorial debut Ex Machina, and with his sophomore film Annihilation, he got more ambitious and way more hallucinogenic. The story follows five scientists who venture into a mysterious, science-bending stretch of land known as Area X where discover all manner of exquisite and terrifying biological aberrations. Garland and his creative team do stunning work bringing the singular terrors of The Shimmer to life in breath-taking detail -- be it a moment of beauty that gives a hitch in your throat to all-out existential terror that knocks the wind out of your lungs. But Anniliation's most transcendent moments are deeply rooted in metaphor, exploring the human propensity for self-destruction with elegantly structured sequences of overlapping visual, narrative and thematic beats so that the whole sprawling, cosmic affair spirals inward, striking at the soft spots of the human experience. The end may be too far out a for some, but Garland proves his canny gift for genre storytelling once again in one of the most challenging, rewarding, and downright ballsy sci-fi movies ever made.

23. RoboCop

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Image via Sony

Part Jesus allegory, part corporate satire, all Paul Verhoeven. The irreverent director applies his wry wizardry to police privatization with the story of a Detroit cop who's resurrected and rebuilt after dying violently in the line of duty. Without his memories or sense of identity, officer Alex Murphy (Peter Weller) becomes a ferocious force for law and order -- at least as it's programmed by the people who own him. While offering commentary on corporate clean-up of street crime, Verhoeven also delivers a delightfully pulpy revenge tale as Murphy starts to regain his memories and makes it his mission to eliminate the ruthless criminals who murdered him (including a gleeful, scenery mangling Kurtwood Smith). Verhoeven's great trick is his skill at navigating tricky tonal terrain, knowing exactly when to blunt the impact of tragedy and sharpen the prod of wit. RoboCop is an energetic and joyful evisceration of corrupt social systems and big business tactics, while also being a downright bombastic sci-fi actioner about one badass cyborg.

22. Looper

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What is time travel without a little paradox? Like most films in the time travel subgenre, if you scrutinize Looper too hard, you're going to run into some logical roadblocks. But unlike the multitudes of inferior films, Rian Johnson's Looper builds a world so immersive and evocatively drawn, the timeline will be the last place you want to look. Looper tells of a future where time travel has been invented but immediately outlawed, used only by organized crime syndicates to send marks back in time and dispose of the bodies without a trace. The plot follows a hitman known as a Looper (Joseph Gordon-Levitt), whose life is thrown into chaos when his older self (Bruce Willis) becomes the one target he can't execute.

The first half of the film is an inventive spin on familiar tropes with a welcome flair for world-building, but ultimately its purpose is to establish time travel as a narrative framing device for the surprising core of complex family drama in the second half. Johnson is the kind of skilled filmmaker that knows the rules so well, he knows exactly how and when to break them, and as a result, Looper is filled with moments of delightful surprise. Johnson takes great pains to ensure his film closes its own loop elegantly, and he's willing to go surprisingly dark to get there. Looper is still a few years out from being recognized as the modern sci-fi classic it is, but no doubt time prove the film's staying power.

21. Her

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A story about a modern man who falls in love with his operating system sounds about as on-the-nose as it gets, but in the hands of writer-director Spike Jonze, it's a poignant and perceptive look, not only at our dependent relationship with technology but the ephemeral nature of romantic connection and the ways we cling to each other out of fear of loneliness. Jonze paints an unusual portrait of the future in that it actually looks like a nice place to be. Warm-toned, perhaps a bit crowded, but ultimately a slightly more beautiful version of the world we live in now.

When the first A.I. is introduced to the world, Theodore (Joaquin Phoenix), a man devastated by his recent divorce, downloads and meets Samantha (Scarlett Johansson), a charming and kind consciousness beyond his comprehension who is discovering herself with each new second. Before long, they fall in love, but as you might imagine, it's a tricky romance and one that leaves broken hearts behind as Samatha continues to embrace her alternate experience of life and love. Johansson is nothing less than exquisite, creating a character out of nothing but sound -- not even an animated avatar as most voice actors have. While Theodore and Samantha's romance may be uncomfortable and strange, it's earnest, and Jonze treats it with dignity, opening up ponderous avenues of thought on the future of human intimacy. Her is a gorgeous treatise on loneliness and the desire for connection that avoids easy terrain in favor of a quiet thoughtfulness that reveals how our growing intimacy with technology makes us more human than ever.

20. Moon

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Duncan Jones' 2008 directorial debut is an instant sci-fi classic. Physically contained but conceptually grand, the film follows Sam Rockwell as an astronaut working alone on the moon who stumbles onto a dreadful truth that calls his whole reality into question. That's about as vague as plot summaries get, but to reveal any more is to ruin the countless surprises that lie ahead, as each new reveal redefines your concept of the film and its stakes. Jones has plenty to say about corporate ruthlessness in his tale of the lonely moon man, but if Moon's concepts are impressive, it's the character drama that cements the film as an all-timer. Aside from some faces on the video screens and a lovable low-tech robot voiced by Kevin Spacey, Rockwell carries the entire film on his back with a remarkable performance. The film demands extreme nuance and screen presence from its star, and Rockwell delivers at every turn, keeping the audience on track with the twisty plot without ever having to spell it out for them. Moon is a fearlessly smart film that has faith you'll keep up, and the rewards are only greater for it.

19. Starship Troopers

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Image via Sony Pictures

One of the most famously misunderstood films of all time, Paul Verhoeven's Starship Troopers is a cheeky skewering of fascist militarism dressed up in propagandist splendor. Pitch perfect camp with moral messages hiding just below the blood, guts and tits, Starship Troopers reteams Verhoeven with RoboCop writer Ed Neumeier to repurpose Robert A. Heinlein's 1959 novel as a tactical takedown of the jingoistic military machines, littered with the body parts of the young soldiers they spits out on the never ending path to victory.

The film follows a trio of eager teenage recruits led by Johnny Rico (Casper Van Dien) as they work their way up the various branches of the military industrial complex. Shipped off to do battle with an alien race of giant bugs (provoked to war by Earth's intergalactic colonization), the disposable infantrymen are tossed into the meat grinder again and again, but they never waiver in their xenophobic convictions. Taken at face value, the film is a teenage boy's dream, equipped with splattery gore, lurid spectacle, and even a love triangle, but look just beneath the superficial escapism and it's easy to see the shades of Orwellian subversion.